We propose to study the protein composition of normal middle ear fluid and compare these results with fluids derived from patients with secretory otitis media. Special attention will be given to the quantitation of immunoglobulins and to the presence of the secretory IgA. Using antisera specific for secretory component (SC) the concentration of secretory IgA and free SC will be quantitated in different fluids. An immunofluorescent study of normal tissues and tissues from patients with secretory otitis media will be performed. Attempts will be made to determine the immunoglobulin class in paired serum and middle ear fluids of specific antibodies such as those against the polio virus. Tissues and cells derived from middle ear fluids will be examined for the occurrence of delayed hypersensitivity reactions. Antisera are already available against 5 secretion specific components isolated from other nonvascular fluids such as urine, colostrum, and amniotic fluid. Using these antisera we will examine middle ear fluids both qualitatively and quantitatively for these components. The tissue synthesis and localization of these components will be studied using in vitro organ culture and immunofluorescent techniques. Our overall objective is to determine whether the secretory immune system is operative in the middle ear mucosa and also to acquire information concerning the types of macromolecules synthesized by the middle ear and possible abnormalities in these proteins which occur in secretory otitis media.